I recall being on a Boy Scout campout, and one of the guys tied a huge number of tea bags to the end of a rope and lowered it into about 1" of water in the standard Boy Scout coffeepot. I think he did it just to see what would happen.
The black stuff that came out definitely needed more water.
Ah, but the key phrase here is “normal strength”, and for that, time is an important variable. For a standard ratio of 1 bag per cup, you need to remove the bag after a set time, lest it become overbrewed. So a single teabag is capable of going beyond “normal strength” tea.
So, if a single bag were left indefinitely, would it saturate at the same strength as more teabags? (though with more teabags you’d get you there faster of course.)